Removing the disturbances at VLF signals with developed a software

Very Low Frequency (VLF) radio waves are guided by spherical waveguide formed between the Earth?s surface and the lower edge of the ionized portion of the atmosphere. This waves are in the range of 3 kHz to 30 kHz and can efficiently propagate across long distances. In this thesis, Using MATLAB gui an interface was designed. This interface is based on wavelet transform and filtering based methods to denoise disturbances of VLF signals . VLF receiving system is established in Science Faculty of Fırat University. VLF signals are recorded by this system. With this interface, our goal is realizing wavelet transform ve filtering based methods to denoise at VLF signals. For wavelet transform, wavelet types and levels are selected, approximation and detail coefficients determined and this coefficients are plotted on graphics. Also, thresholding types, threshold selection rules, scalling types, wavelet types and order are selected. Finally, original VLF signals and denoised VLF signals are plotted to interface. Filtering based methods (FIR or IIR Filters) are used to denoise at VLF signals. For FIR filter window function, filter order and cutoff frequency are selected, later VLF signals, FIR filter and denoised VLF signals are plotted on interface. Similarly, for IIR filters one of (Butterworth, Chebyshev I, Chebyshev II ) filters type, filter order and cutoff frequency is selected. Finally, original VLF signals and denoised VLF signals are plotted to interface.